github actions: Switch to multiline string format suggested by GA docs

[bmastbergen]

The validate-kernel-commits github action has the following errors:

Error: Process completed with exit code 1.
Error: Unable to process file command 'output' successfully.
Error: Invalid value. Matching delimiter not found ''EOF''

Switch to the multiline string format suggested in the github action documentation here:
https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-commands#example-of-a-multiline-string

Sorry I missed these during the initial review process of this workflow. They were not obvious in the runner output.

[PlaidCat]

I am good with the keeping the EOF from the original way of the commit and not the thread.

[kerneltoast]

Note to self: EOF quotes can't be used because GH actions don't seem to fully implement the shells they claim to use... or I guess the GITHUB_OUTPUT parser is something they rolled themselves that doesn't run in your specified shell.

🚢